The present invention relates generally to a system for testing integrated circuits (ICs), and, more particularly, to a method and apparatus for high speed testing of ICs having either logic circuits, memory arrays or both.
Manufacturers in the electronic industry use test systems to automatically test various electronic components and integrated circuits (ICs) to weed out defective devices or ICs. Broadly, there are two types of test systems, those suitable for testing memory arrays or circuits, such as flash memory or Random Access Memories (RAM), those suitable for testing logic circuits, such as Micro Controllers, Application Specific ICs (ASICs), and Programmable Logic Devices (PLDs). Generally, it is desirable to test the ICs at several points during the manufacturing process including while they are still part of a wafer or substrate and after packaging the devices before they are mounted or assembled on modules, cards or boards. This repetitive testing imposes demands on test systems to automatically perform tests at high speed and with a high degree of accuracy. Moreover, the trend in the electronic industry has been to further increase the miniaturization of electronic devices and circuits, thereby allowing for an increase in the complexity of the IC. Thus, as ICs become more complex, the complexity of the test systems must increase correspondingly.
An example of part of a prior art logic test system 10 for testing logic circuits in an IC, commonly known as a Device Under Test or DUT 12 having a number of pins 14 is shown in FIG. 1. Referring to FIG. 1, test system 10 typically includes a general purpose computer 16 or PC, a clock 18, logic vector memory (LVM 20) with a sequencer, a number of timing and format circuits (T/Fs 22), and a number of pin electronics or P/E channels 24. Computer 16 loads test programs and controls operation of other components of test system 10. Clock 18 generates system clocks and the test system period, which are provided to LVM 20, T/Fs 22, and other pipeline circuits in the test system. LVM 20 stores and sequences test signals, commonly known as test vectors, used during the testing process. T/Fs 22 adjust the timing and formatting of various signals, i.e., data, strobe and input/output (I/O) control signals, received from LVM 20 and couple the LVM to DUT 12, through PE channels 24. It should be noted that although test system 10 may include a single computer 16, clock 18 and LVM 20, it generally includes one T/F 22 and an associated P/E channel 24 for each pin 14 on a DUT 12, shown here as having pins 1 through n.
PE channels 24 typically include a PE driver 26 for applying a test vector, data, to a pin 14 of DUT 12, a comparator 28 for comparing a DUT output signal with an expected output signal, and an error logic circuit 30 for coupling results of the comparison back to error processing circuitry and and an error capture memory (not shown). Generally, PE driver 26 and comparator 28 are not active in the same PE channels 24 at the same time, since pin 14 is either receiving data or control signals or transmitting a result at a given time. PE channels 24 further include a data line 32 for coupling the test vectors from T/F 22 to PE driver 26 and error logic 30, an enable or control line 34 for enabling the PE driver to apply the test vector to DUT 12, and a strobe line 36 for enabling error logic 30.
An example of part of a prior art memory test system for testing memory arrays in DUTs is shown in FIG. 2. Referring to FIG. 2, the test system 38 typically includes a computer 40, a clock 42, an algorithmic pattern generator (APG 44), T/Fs 46, and P/E channels 48, 49, 50. APG 44 is used for generating a test signal or test vector for testing the memory array in the DUT. As above, it is to be noted that test system 38 further includes a single computer 40, clock 42 and APG 44, but a number of T/F 46 with associated P/E channel 48, 49, 50 for each pin on a DUT (not shown). For purposes of clarity, FIG. 2 illustrates only three T/Fs 46 and PE channels 48, 49, 50. PE channel 48 and PE channel 49 differ from PE channel 50 because they merely provide address and clock signals to the DUT and therefore require only a PE driver 52. PE channel 50 both provides data to and receives data from a pin on the DUT, and therefore includes, in addition to PE driver 52, a comparator 54, an error logic circuit 56 that functions as described above. PE driver 52 is coupled to T/F 46 by data line 58 and control line 60. Comparator 54 and error logic 56 are coupled to T/F 46 by strobe line 62 and data line 58.
A fundamental problem with the above test systems 10, 38 is their inability to easily test in parallel DUTs having a combination of both logic circuits and memory arrays.
Another problem with the above test systems 10, 38, is their inability to switch the pattern source signal coupled to the pin at least twice in each DUT cycle.
Yet another problem with the above test systems 10, 38, is their difficulty in testing DUTs having serial data paths.
Still another problem with the memory test system 38 described above, is the inability to route any output from the APG 44 to any PE channel 48, 49, 50, and therefore to any pin on the DUT. For example, in a test system 38 designed to accommodate 64 pin ICs, outputs from an address T/F may be mapped to any one address of address pins one through twenty-four, while outputs from a data T/F would be mapped to data pins twenty-five through fifty-six, and outputs from a clock T/F are mapped to pins fifty-seven through sixty-four. Thus, it is difficult if not impossible to reconfigure the test system 38 to accommodate DUTs having a different number of pins and/or arranged in a different configuration.
The present invention is directed to an apparatus and method for high speed testing of integrated circuits (ICs) having either logic circuits, memory arrays or both.
In one aspect, the present invention is directed to an apparatus for testing a device under test (DUT). Generally, the apparatus includes: (i) a pattern generator having a number of outputs for outputting signals for testing the DUT; (ii) a number of pin electronics channels (P/Es) each coupling to one of a number of pins on the DUT; (iii) a number of timing and format circuits (T/Fs) for mapping signals to at least one of the P/Es; (iv) a pin scrambling circuit connected between the pattern generator and the T/Fs, the pin scrambling circuit capable of mapping at least two signals from any of the pattern generator outputs to any one of the T/Fs; and (v) a clock for providing a clock signal having a clock cycle to the pattern generator and the T/Fs. Preferably, the T/Fs are capable of switching the signals coupled to the P/Es at least twice in a clock cycle.
In one embodiment, the pattern generator includes logic vector memory (LVM) for testing logic circuits, and a memory signal source, such as an algorithmic pattern generator (APG), for testing memory arrays, and the scrambling circuit is capable of mapping signals from the LVM and the APG to separate T/Fs, thereby enabling the apparatus to simultaneously test one or more DUTs having logic circuits, memory arrays or both. Alternatively or additionally, the pattern generator can include a scan memory for serial type test interfaces or structural test.
In another embodiment, the pin scrambling circuit is capable of sequentially coupling signals on a number of the pattern generator outputs, generated in parallel, to one of the P/Es to test a DUT having a serial input. In one version of this embodiment, the pin scrambling circuit is capable of simultaneously coupling a number of signals to other pins on the DUT to simultaneously test DUTs having both serial and parallel inputs, such as for example NAND flash memories.
In another embodiment, a number of the apparatuses are capable of being linked to form a test system that can test DUTs having a number of pins at least greater than the number of the P/Es on any one of the individual apparatuses.
In another aspect, the present invention is directed to a method of testing a DUT using an apparatus having a clock, a pattern generator having a number of pattern generator outputs, and a number of pin electronics channels (P/Es). In the method, a clock signal having a clock cycle is provided using the clock, and signals for testing the DUT provided on the plurality of pattern generator outputs using the pattern generator. Each of a number of pins on the DUT are connected to one of the P/Es, and a signal from the plurality of pattern generator outputs coupled to at least one of the P/Es. The signal coupled to the P/E is switched at least twice each clock cycle, thereby providing an effective testing rate at least twice that of the clock cycle.
In one embodiment, the apparatus further includes a number of T/Fs each coupled between the pattern generator and one of the P/Es, and the step of coupling a signal to at least one of the P/Es involves coupling a signal from a T/F to at least one of the P/Es. In one version of this embodiment, the apparatus further includes a pin scrambling circuit connected between the pattern generator and the T/Fs, and the step of switching the signal coupled from the pattern generator outputs to the P/Es involves mapping at least two signals from of any of the pattern generator outputs to one of the T/Fs.
In another embodiment, the pattern generator includes logic vector memory (LVM) for testing logic circuits, and an algorithmic pattern generator (APG) for testing memory arrays. In this embodiment, the step of coupling a signal from the pattern generator outputs to the P/Es involves coupling signals from the LVM and the APG to separate or the same P/Es, thereby enabling simultaneous testing of one or more DUTs having both logic circuits, memory arrays or both.
In yet another embodiment, the step of coupling a signal to the P/E includes the step of sequentially coupling signals from pattern generator outputs to one of the P/Es to test a DUT having a serial input. In one version of this embodiment, signals are simultaneously coupled from a number of the pattern generator outputs to other pins on the DUT to test DUTs having both serial and parallel inputs, such as NAND flash memories.
The advantages of the present invention include: (i) the ability to couple any output on a pattern generator to any pin on a DUT, and to switch the signal coupled to the pin at least twice in each clock cycle; (ii) the ability to have a plurality of mappings selectable on a cycle-by-cycle basis; (iii) the ability to quickly and easily reconfigure the apparatus or test site to test one or more DUTs having logic circuits, memory arrays or both; (iv) the ability to quickly and easily reconfigure the test site to test one or more DUTs having serial data paths by serializing test signals generated in parallel using the pin scrambler and coupling them to any pin on a DUT; (v) the ability to quickly and easily reconfigure the test site to test DUTs having serial data paths, parallel data paths or both; (vi) the ability to quickly and easily reconfigure the test site to route serial scan memory to any pin or set of pins on a DUT, and change the routing at least twice in each clock cycle; (vii) the ability to quickly and easily reconfigure the test site to simultaneously test in parallel multiple DUTs each having a number of pins less than half the available P/E channels by mapping the same pattern generator outputs to multiple sets of P/E channels; and (viii) the ability to quickly and easily link multiple test sites to enable the testing of a DUT having a number of pins greater than the number of the P/Es available on any one or more of the individual test sites.